Multi-objective Optimization Of Phtothermal And Photovoltaic Combined Cooling,Heating And Power System Based On Nsga-Ⅱ Algorithm

Multi-energy complementary distributed energy supply system is an important way to realized the technological change of energy utilization.Among a variety of renewable energy sources,solar energy has great application prospect,showing strong flexibility when coupled with distributed energy system.Based on the above background,this paper proposes a photothermal and photovoltaic combined cooling,heating and power system,and studies the capacity configuration and operation regulation of the coupling system.The main research contents and conclusions are as follows:(1)Firstly,the structure design of the coupling system is carried out to clarify the internal energy flow relationship of the system and formulate the system operation strategy.The general mathematical model of the coupling system represented by the trough heat collecting unit was established,and the model was verified from two aspects of light gathering performance and heat collecting performance,and the error of the model was less than 3%,which met the accuracy requirements.(2)Taking an office building in Shanghai as an example,a multi-attribute optimization objective based on annual cost saving rate,primary energy saving rate and carbon dioxide reduction rate was established,the NSGA-II algorithm was used to conduct multi-objective optimization of the coupling system with different energy storage modes(heat storage,heat storage + electricity storage)and it was compared with the distribution system.The results show that,compared with the reference system,the coupling system has good energy and environmental benefits,and the primary energy saving rate of the optimized coupling system is up to 41.44% and 46.12%,respectively.The system’s energy and environmental performance improved by 4.68% and 5.46% respectively with the access of battery cells.(3)The system decision was made based on the comprehensive performance evaluation index of the coupling system,and the running state and performance of the coupling system were analyzed based on the selected the appropriate scheme from multiple levels.The results show that the two coupling systems can match the hourly load requirements of end-users well,and the energy loss probability of the system is reduced by about 2.5% with the connection of battery units.In summer,the coupling system has better economic performance,and the annual cost saving rate is about 10%higher than that in winter,while in winter,the coupling system has better energy and environmental benefits,and the primary energy saving rate and carbon dioxide emission reduction rate are more than 30%.(4)The sensitivity analysis of the coupling system was carried out based on the factors of environment,load and energy,and the multi-objective optimization comparison of the coupling system with different load characteristics and different energy prices was carried out.The results show that the fluctuation of power price has a greater influence on the economic performance of the coupling system.The annual cost saving rate of the coupling system increases by 1.59%(heat storage only)and 1.73%(heat storage + electricity storage)for every 5% increase in the average electricity price.In the end users dominated by the cooling/electrical load,the overall performance of the coupling system is poor.For example,the energy and environmental benefits of the coupling system in the optimization result of shopping malls are mostly less than 20%.In the end user dominated by cold/heat load,the photothermal system is dominant,but the addition of battery units will damage the overall performance of the system.